Tìm số nguyên x biết 7 - x = 8 - (- 7)

7 - x = 8 - (- 7)

7 - x = 8 + 7

7 - x = 15

x = 7 - 15

x = -8

1)Tìm x thuộc z biết

a)x+15=18-(-27)

b)-x+7=28

c)20-(-x)=14

d)2x+5=x-14

e)x+17=-8-20

f)3x+15=2x+6

2)Tìm a thuộc z biết

a)/a+3/=/-5/

b)/a-1/=2+/-3/

c)/a+1/=/2a-1/

nhanh để mai mình đi học nha các bạn

a) \(x+15=18-\left(-27\right)\)

\(\Leftrightarrow x+15=18+27\)

\(\Leftrightarrow x+15=45\)

\(\Leftrightarrow x=45-15\)

\(\Leftrightarrow x=30\)

b) \(-x+7=28\)

\(\Leftrightarrow-x=28-7\)

\(\Leftrightarrow-x=21\)

\(\Leftrightarrow x=-21\)

c) \(20-\left(-x\right)=14\)

\(\Leftrightarrow20+x=14\)

\(\Leftrightarrow x=14-20\)

\(\Leftrightarrow x=-6\)

d) \(2x+5=x-14\)

\(\Leftrightarrow2x+5-\left(x-14\right)=0\)

\(\Leftrightarrow2x+5-x+14=0\)

\(\Leftrightarrow x+19=0\)

\(\Leftrightarrow x=0-19\)

\(\Leftrightarrow x=-19\)

e) \(x+17=-8-20\)

\(\Leftrightarrow x+17=-\left(8+20\right)\)

\(\Leftrightarrow x+17=-28\)

\(\Leftrightarrow x=-28-17\)

\(\Leftrightarrow x=-\left(28+17\right)\)

\(\Leftrightarrow x=-45\)

f) \(3x+15=2x+6\)

\(\Leftrightarrow3x+15-\left(2x+6\right)=0\)

\(\Leftrightarrow3x+15-2x-6=0\)

\(\Leftrightarrow x+9=0\)

\(\Leftrightarrow x=0-9\)

\(\Leftrightarrow x=-9\)